Abstract
In this paper, a fiber probe high-temperature sensor based on the Michelson Interferometer (MI) is proposed and experimentally verified. We used a fiber splicing machine to fabricate a taper of the single-mode fiber (SMF) end. The high order modes were excited at the taper, so that different modes were transmitted forward in the fiber and reflected by the end face of the fiber and then recoupled back to the fiber core to form MI. For comparison, we also coated a thin gold film on the fiber end to improve the reflectivity, and the reflection intensity was improved by 16 dB. The experimental results showed that the temperature sensitivity at 1506 nm was 80 pm/°C (100 °C~450 °C) and 109 pm/°C (450 °C~900 °C). The repeated heating and cooling processes showed that the MI structure had good stability at a temperature up to 900 °C. This fiber probe sensor has the advantages of a small size, simple structure, easy manufacturing, good stability, and broad application prospects in industrial and other environments.
Highlights
Operation Principle and Device FabricationWhen the light propagates in single-mode fiber (SMF), the high-order modes are excited at the taper, so different modes are transmitted forward in the fiber, reflected by the end face of the fiber, and recoupled back to the fiber core at the taper to form Michelson Interferometer (MI)
(100 ◦ C~450 ◦ C) and 109 pm/◦ C (450 ◦ C~900 ◦ C)
As early as 2004, D Grobnic et al proposed a high-temperature stable Bragg grating that has been inscribed in sapphire fibers and has been tested as a sensor for temperatures up to 1700 ◦ C [16]
Summary
When the light propagates in SMF, the high-order modes are excited at the taper, so different modes are transmitted forward in the fiber, reflected by the end face of the fiber, and recoupled back to the fiber core at the taper to form MI. Its interference can be expressed by the general formula:. Where I1 and I2 represent the light intensity of the respective core mode and high-order cladding mode transmitted in the SMF. )2L n and n represent the effective refractive index of the core mode and the cladding mode, respectively, L represents the distance from the taper to the end face of the fiber, λ represents the input light wavelength, and m represents the m-order cladding mode
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